Most automotive vehicles include an internal combustion engine as the sole power source for providing drive torque to one or more sets of wheels. To achieve a variety of environmental and fuel economy goals, some vehicles have been configured to include multiple sources of motive power. In one known example, a hybrid vehicle utilizes an internal combustion engine and an electric motor. The internal combustion engine and the electric motor can separately or in combination to provide power to one or more axles through a common driveshaft coupled to a differential. Vehicles of this type are often referred to as series-hybrid vehicles. While this arrangement may have merit, unless some form of traction control is implemented, wheel slippage may occur at the wheel with the lowest traction. Furthermore, the differential may be relatively costly and add undesirable weight to the vehicle.
Another known hybrid vehicle includes single or multiple electric motors connected to one or more axles, where an internal combustion engine is used for driving a generator for providing electrical power to the drive motor or motors. An alternative driving an axle via a costly and relatively heavy differential is to fit each wheel with individual electric motors. Unfortunately, this arrangement adds an unacceptable amount of unsprung weight to each wheel. Vehicles of this type are often referred to as series hybrid vehicles.
A further known hybrid vehicle includes an internal combustion engine for providing drive torque to a first axle and an electric motor for providing drive torque to a second axle. The vehicle can be driven by the internal combustion engine, by the electric motor, or by both the internal combustion engine and the electric motor. Vehicles of this type are often referred to as full hybrid vehicles.
Hybrid vehicles are often provided with a generator driven by the internal combustion engine or with a starter generator mounted on the internal combustion engine in order to supply power to the electric motor or to charge a battery pack. The battery pack is used for driving the electric motor, driving auxiliary equipment, such as an air conditioning unit, or for starting the internal combustion engine.
A problem with hybrid vehicles provided with a hybrid drive arrangement comprising a battery pack of this type is that the plug-in hybrid electric vehicle may become inoperative should the battery pack develop a fault. This is a particular problem for plug-in hybrid electric vehicles. Accordingly, there is a need for alternative hybrid drive arrangement complementing the existing internal combustion engine and electric power transfer systems.